1. Field of the Invention
This invention relates to a laminated chip-type LC filter suitably used as a noise filter, for example, for EMI and the like.
2. Description of the Related Art
Conventionally, a noise filter has been so constructed that an inductor L and capacitors C are assembled into an L-type, .pi.-type or T-type in order to raise impedance against noise, or to bypass a component of noise to ground.
There are two types of conventional LC filters; one is the type in which separate parts serving as inductor L and capacitors C are connected together, and the other is the laminated chip-type filter.
The laminated chip-type LC filter has a filter body, obtained by sintering integrally laminated members comprising magnetic material green sheets and dielectric green sheets to form magnetic material and dielectric sections, external electrodes at both ends thereof, a ground on at least one of upper and lower surfaces thereof, a conductive layer connected to the external electrodes at both ends thereof and located within the above-described magnetic material, and internal electrodes having respective ends thereof connected to the external electrodes and located within the dielectric section opposite the ground.
The LC filter, in which separate parts serving as inductor L and capacitors C are connected together, poses problems in that it is relatively large, exhibits low mounting density when fixed to a printed substrate, and moreover, requires much assembly time in its manufacture.
In addition, another problem occurs in that, when a lead terminal connected to the ground is longer than necessary, the noise elimination effect is remarkably deteriorated due to lead inductance thereof.
In the laminated chip-type LC filter, problems having occurred in the LC filter of the former type are obviated, but stray capacitance between both terminals of the chip has reduced considerably the high-frequency characteristic thereof.